| Also known as | T2259 |
| Diagram | Fig. 2 — CRANKCASE · ref 38 |
| Subsystem | primary |
| Listed in parts books | 1969–1971, 1973–1974, 1976–1979, 1985 |
Drain and adjuster plug
Drain and chain-adjuster access plug for the Triumph primary chaincase, 7/16-14 UNC.
This is the drain and adjuster plug that lives in the outer primary chaincase, doubling as the oil drain point and the access hole for the chain tensioner adjustment. Pull it and you can check or reset primary chain tension without splitting the cover, then use the same hole to let the primary oil out when it's time for a change. The legacy T2259 number is the same physical part under the old letter-prefix scheme.
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It shows up across a wide run of catalog years and appears in multiple primary and chaincase figures, so it's a part that stayed pretty much the same through a long production run. Thread spec on this one is 7/16-14 UNC.
Keep the old sealing washer or fit a fresh one when you put it back in, since the plug sits right at the bottom of the chaincase where any leak shows up fast.
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